1. Field of the Invention
The present invention relates to buffers for a switch fabric for inter-connection between multiple modules in a communication system.
2. Description of the Related Art
A network switch is a data switching device that forwards a data unit (“packet”) from a source network component to a destination network component. Typically, a network switch receives a packet from the source network component via an input port and sends a packet to the destination network component via an output port. A network switch for packet switching might be implemented as a crossbar switch. A crossbar switch (also known as a “crosspoint switch” or a “matrix switch”) inter-connects a plurality of input ports and output ports to each other. A crossbar switch having P inputs and Q outputs has a switch fabric matrix with P×Q crosspoints where connections between input ports and output ports are made. Packets arriving at one of the input ports might be routed to one or more specified output ports. For example, a packet might be routed to just a single specified output port (unicast), routed to all output ports (broadcast), or routed to multiple specified output ports (multicast).
Some crossbar switches might employ switch fabric speed-up, meaning that the internal data rate of the switch is higher than the data rate of the input and output links. Speed-up might be implemented by employing a wider data bus within the switch fabric than the data bus for the input and output ports. For example, a switch fabric might have input and output (I/O) ports with a data bus width of N, and the switch fabric might have a data bus width of m*N, where m is the speed-up factor. A crossbar switch might employ first-in, first-out (FIFO) I/O buffers at each input and output port to facilitate re-sizing data packets between the bus width of an I/O port and the switch fabric. The I/O buffers might beneficially employ dual port memories to allow simultaneous reads and writes of the memory. However, dual port memories can be expensive, and thus might not be available for implementations requiring large buffers.